German patent no. 4135570 C1 describes a sealing band for wrapping around a cable passing through a duct, to create a seal between the cable and the duct, in which at least the inside of the band turned towards the cable has a roughened surface, preferably formed from projecting friction elements. The friction elements may be fine-grained corundum or emery, or they may be metal or plastic and anchored in the material of the sealing band.
International patent application WO 94/05935 (Raychem) discloses a sealing member comprising (a) a sealing material having a cone penetration between 80 and 400 (10.sup.-1 mm) and an ultimate elongation of at least 100%, and (b) an elastomeric retaining member for the sealing material.